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Wednesday, April 30, 2014

Capturing the Light: Starbursts

Creating a Starburst
In the course of posting some of my shots throughout the past few days, I’ve had some people ask me how I get the starburst effect with the sun. For example, look at the sun in this early morning sunrise photo where I was looking across the Tidal Basin towards the Jefferson Memorial in Washington D.C.



The answer of how to achieve this is pretty simple, although the technique requires a little practice to be able to pull it off in the manner you may want to. All you need to do is to use a small (numerically high) aperture. In the case of the photo above, I used f/22.

Of course using such a high f-stop can bring other factors into the equation. I used an ISO of 100 and a shutter speed of 1/30 sec. While in theory I should be able to handhold that reasonably well at 17mm, I did use a tripod. After all, if you’ve went through the trouble of getting up at 4:00am to stake out a claim for a Tidal Basin sunrise during the peak bloom for the cherry blossoms, do you really want to leave anything to chance? So keep in mind that a tripod may be required when trying to pull this off, depending upon the circumstances.


Starbursts at Night
This is especially true when shifting from a light source such as the sun to something like street lights, as in the following example:



This photo of the U.S. Botanical Gardens was taken from the west side of the U.S. Capitol, looking back across the reflecting pool. I used an f-stop of f/20 on my 70-200mm f/4L IS USM, and again I used an ISO of 100. Shutter speed was 30 seconds, so even with an IS lens, you aren’t going to handhold that! So always keep your tripod in mind. Of course, if you are using a tripod, it’s best to couple its use with a remote trigger and mirror lockup.


Starbursts and Silhouettes
Once you understand the basics above, you’ll find there’s much more you can experiment with. One thing I often like to do, is to combine a silhouette with a starburst.  The starburst becomes the focal point of the image, and contrasts nicely against the silhouette. See the following example of a photo from a couple of weeks ago using the U.S. Capitol.



Since there was plenty of light available for this photo, and I was going to be underexposing to make the foreground a silhouette, handholding was an option this time. The shot settings were f/22, ISO 400, and a shutter speed of 1/1000 of a second.

However, there are a couple of other tricks I used here. I shot this in Aperture Priority mode, allowing me to set f/22 and the camera look for the “proper” exposure. Since I wanted to underexpose the U.S. Capitol to be a silhouette, I used the camera’s spot metering mode, and metered a little to the right of the sun. This forced the camera to use a higher shutter speed than if I had used another metering mode, or if I would have spot metered off of the Capitol.

I then composed the image so that the sun was partially obscured by the Capitol’s dome, making the starburst really stand out against the dark silhouette. Sometimes, as with this shot, I may dial in a little more exposure compensation to further darken the silhouette. In looking back at the EXIF data, I had this image underexposed by another 1/3 of a stop.

Keep in mind that the light falloff will be pretty dramatic in a silhouette image such as this. Most of the time that brings the viewer eye back to the starburst being the main focal point of the image though, which is what you are likely after.


A Few Final Thoughts
I should also mention that there is a filter called a cross-screen filter that can also be used to produce the starburst effect. However, using a small aperture allows you to create this effect without the need to purchase any additional items. Unless you course you don’t have a camera or lenses, and in that case why are you even reading this article to begin with?

Also keep in mind the limitations of your equipment. While your lens may be capable of f/32, the use of an extremely small aperture can cause degradation in the image quality due to what’s called diffraction. Of course diffraction is actually produces the starbursts to begin with, but there can be a point where it starts to affect the sharpness throughout the rest of the image. Because of this, I will normally limit myself to f/20 or f/22, although some people use a maximum of f/16 or so. I haven’t seen much of a difference up to f/22 with my images, but that will vary depending upon the subject and circumstances.

I should also mention the possibility of lens flares before I conclude this article. If you are using budget lenses, you’re likely going to see some lens flare, especially if shooting into the sun. Even the best lenses will suffer this fate depending upon the sun’s angle and time of day, although to a lesser extent. If you want this effect, that’s great, but otherwise you’ll have to remove them later when you post process. Most of the time you can minimize lens flare substantially by partially obscuring the sun with an object, like I did with the Capitol silhouette photo. Also, it’s a good idea to remove any filters you have on the end of the lens, as they can increase the possibility of flares as well. This is especially true with cheaper filters.

Last of all, if you are going to be using the sun to produce the starburst effect, you avoid looking directly into it. It’s tough to avoid I know, especially depending on the time of the day. However, you’ll find with practice you’ll become faster at getting the shot and the whole process will be a little more intuitive and easier to accomplish.